calul.c: In function ‘main’:
calul.c:13: warning: incompatible implicit declaration of built-in function ‘strlen’
calul.c:22: error: invalid lvalue in unary ‘&’
calul.c:22: error: expected ‘)’ before ‘r’
calul.c:61: error: expected ‘;’ before ‘}’ token
calul.c:61: error: expected declaration or statement at end of input